STABILITY TESTS FOB 


NITROCELLULOSE AND 


NITROCELLULOSE POWDERS 



ALBERT F>. SY, M. -S. 


Assistant Chemist, Ordnance Department, U. S. A. 


Frankford Arsenal. 





REPRINTED FROM 


“JOURNAL OF THE UNITED STATES ARTILLERY” 


SEPTEMBER—OC TOBER, I 903 



456V'> 



FORT MONROE, VA., 
ARTILLERY SCHOOL PRESS, 




0 














* 







JOURNAL 


OF THE 

UNITED STATES ARTILLERY. 


Vol. XX. No. 2. SEPTEMBER—OCTOBER 1903. Whole No. 63. 


STABILITY TESTS FOR NITROCELLULOSE AND 
NITROCELLULOSE POWDERS. 

By ALBERT P. SY, M.S. 

Assistant Chemist, Ordnance Department, U. S. Army. 

Frankford Arsenal. 


Stability tests, sometimes also called “heat tests,” are applied 
to explosives to determine their keeping qualities, or chemical 
stability. The manufacturer also uses some stability tests, dur¬ 
ing manufacture, to determine if his product has been thorough¬ 
ly purified. 

That the stability of an explosive is of the utmost importance 
must be apparent, and it explains why government and explo¬ 
sives chemists have been and are making an exhaustive study of 
the methods for stability testing. Although a great deal of 
work has been done in this direction, yet the best methods in use 
today are still far from ideal. The fault lies in the fact that the 
general cause or causes of instability of explosives have not been 
established.* 

In the early stages of nitro-explosives manufacture, instability 
was frequently caused by traces of nitrating acids left in the 
finished product. Today, with improved methods and apparatus, 
insufficient purification is not the most frequent cause of in¬ 
stability. But. even if purification be perfect, it has been foundt 
that normal products, perfectly purified, may become unstable. 

Among the known causes of instability are the following : 

(1) Traces of nitrating acids left carelessly by the manufac¬ 
turer. (Rare.) 

* Luck & Cross. Jour. Soc. Chem. Ind., 1900, p. 642. 
f Guttmann : Zeitschr. f. Angew. Ch. 1897, p. 233. 


Journal 9. 









STABILITY TESTS KOR NITROCELLU LOSE 


(2) Substances added to powders to increase stability some¬ 
times have the reverse effect. For example, alkalies, added to 
powders for the purpose of neutralizing - traces of nitrating acids 
or acids which might be formed from decomposition of an un¬ 
stable powder, may cause saponification or decomposition ol the 
nitrocellulose itself. The value of alkalies for increasing stabil¬ 
ity is a disputed point.* Saponification may be caused by water. 

• A sample of pure nitroglycerin kept in distilled water has been 
known to develop acidity.f 

(3) Local decomposition may be set up in a powder by careless 
treatment and handling. 

(4) Exposure to higher than usual temperatures, during dry¬ 
ing or storing. 

(5) Cotton wool always contains, even after careful cleaning, 
small quantities of organic substances other than cellulose.£ 
These are nitrated together with the cellulose, forming nitro¬ 
compounds which are quite unstable ; they can not be removed 
by ordinary processes of washing or solution.§ These unstable 
compounds may cause decomposition of the nitrocellulose. 

(6) Various investigators|| hold that even a perfectly pure pro¬ 
duct may decompose slowly, spontaneously ; the products of such 
decomposition may act catalytically and thus bring about com¬ 
plete decomposition. According to this view all nitrocelluloses 
are unstable, or their degree of stability is only relative, depend¬ 
ing upon conditions. 

(7) Spontaneous combustion of organic compounds is believed 
to be caused by intramolecular respiration or oxidation, and it 
seems likely that this might be the cause of spontaneous decom¬ 
positions of nitrocellulose, even if it be perfectly pure. The 
nitrocellulose molecule is comparatively large and the atoms 
loosely held together which would favor decomposition brought 
about by internal oxidation. The difference in stableness of 
different nitrocelluloses could easily be explained by slight dif¬ 
ferences in composition, preparation, handling, and differences 
in physical properties. 

It has been stated*)) that it does not follow that because two 
substances are stable, a mixture of the two will also be stable ; 


* Guttmann : Zeitschr. f. Angew. Ch. 1897, p. 233. 
t Thomas: Zeitschr. f. Angew. Ch. 1899, p. 55. 

1 Abel: Trans. Roy. Soc., i 856 , p. 307. 

2 Luck & Cross : Jour. Soc. Ch. Inrl., 1900, p. 642. 

|| Hoitsema : Zeitschr. f. Angew. Ch. 1899, p. 735. Luck & Cross : Jour Soc. Ch. Inti. 
1900, p. 642. 

Guttmann : Zeitschr. f. Angew. Ch. 1897, p. 233. 



AND NITROCELLULOSE POWDERS. 


c. g ., a stable nitrocellulose and a stable nitroglycerin when 
mixed may produce an unstable mixture ; in such cases, the 
mixture is undoubtedly more liable to internal oxidation than 
are the ingredients before mixing. 

(8) It does not seem unlikely that denitrifying bacteria might 
start a decomposition of nitrocellulose, and preliminary experi¬ 
ments strongly indicate the probability of such decomposition. 
The possibility of bacteria causing a decomposition and conse¬ 
quently instability of nitrocellulose is conceded (private commu¬ 
nications to the writer) by authorities on the subject of denitri¬ 
fying bacteria. These experiments are to be continued at this 
laboratory. 

Stability tests are always made on explosives at higher than 
ordinary temperatures of storage. This is done in order to 
shorten the time required for obtaining results, it having been 
determined by experiments that the stability of a powder or 
nitrocellulose decreases as the temperature to which it is exposed 
increases.* For each method of testing stability it is necessary 
to know the behavior of a good or standard powder with which 
to compare results obtained from other powders. On account 
of the great influence of slight variations in apparatus, reagents 
or manipulations in making stability tests, the results obtained 
by any one test, but by different operators, seldom agree. 

Following is a brief description of the more important stabili¬ 
ty tests now in general use : four of these are used officially at 
this laboratory. None of these tests are entirely satisfactory, 
as will be seen later. There is also given a description of a new 
test, developed at this laboratory : this test has been applied to 
a large number of powders, and has given entirely satisfactory 
results. 

THE POTASSIUM-IODIDE STARCH, OR ABEL TEST, f 

This is the oldest and most extensively used stability test for 
finished products, as well as a purity test used by the manufac¬ 
turer. It is one of the official tests of the Ordnance Department, 
U. S. Army, prescribed^ and made as follows : The sample is 
prepared by cutting into slices 0.02 inch thick, and then exposed 
to the air for at least 12 hours.§. 

* Sy : Jour. Am. Ch. Soc., June, 1903, p. 562. 

f Trans. Roy. Soc., 1 865 , p. 269. 

I “Standard Methods of Chemical Tests of Nitrocellulose, etc.” Ord. Dept., U. S. Army. 

\ Preliminary experiments indicate that better results can be obtained by this test if the 
samples are prepared by turning off thin shavings in a lathe and exposing to air for 24 
hours. In the Navy Department, the samples are prepared by shaving the powder with 
glass, producing very thin shavings, which are then exposed to 45 0 C for 48 hours, and 
then put in a moisture box over night. 


4 


STABILITY TKSTS FOK NITROCELLULOSE 


In testing - nitrocellulose, air-dried samples are taken. 1 -3 
gram is placed in a test tube (6 x x / 2 inch) which is then closed 
by a cork carrying a glass rod, the latter having a hook of plati¬ 
num wire fused in at the lower end (see fig. 7, A). On this hook 
there is suspended a strip of KI-starch paper, moistened to one- 
half its length with a 50 per cent glycerin solution. 1 he position 
of the test paper in the tube is so adjusted that the line dividing 
the dry and wet portions of the paper is on a level with the low¬ 
er edge of the film of moisture expelled from the explosive and 
deposited on the inside of the tube. The tube is immersed m a 
in a bath, the temperature of which is regulated to 65.5' C(±i°) 
for nitrocellulose, and to ioo° C (d=i°) for smokeless powders 
(nitrocellulose powders). The bath (see fig. 1) consists of an 
open water bath in which there is placed a copper vessel contain¬ 
ing water or glycerin ; the copper vessel has a cover consisting 
of three perforated and parallel disks about one inch apart. 1 he 
holes in the upper and middle disk are just large enough to ad¬ 
mit the test tubes, while those in the lower disk are smaller. 
This arrangement serves to hold the tubes all at the same level 
and in a vertical position and is an improvement over the old 
form of apparatus usually used in this test. 

When the bath has reached the required temperature the tubes 
with the samples are immersed, and the test begins at this mo¬ 
ment ; it ends at the appearance of a brown line on the test paper 
at the juncture of the dry and wet portions. For a good nitro¬ 
cellulose this discoloration must not take place in less than forty 
minutes (at 65.5° C) and not less than ten minutes (at ioo° C) 
for a good nitrocellulose powder. Powders containing nitro¬ 
glycerin should stand this test for twenty minutes (at 65.5° C). 
The discoloration of the test paper is due to the action of free 
iodine on the starch, the iodine being liberated from the KI by 
impurities, or products of decomposition* volatilized from the 
explosive. 

This test as described, or with some slight modifications, is 
more extensively used than any other. However, it is of most 
value to the manufacturer, since by careful application of the 
test he can determine whether his products are thoroughly 
purified, and the test could be called a “purity test” more ap¬ 
propriately than a “stability test”. When applied to finished 
products, this test has many weak points, as follows : 

(1) It shows, in cases of decomposition of the sample during 
the test, only the beginning and not the continuation of the de¬ 
composition.f 


* Principally nitrogen oxides and acids. 

tWill: Mittheilungen a. d. Centralstelle f. wissenschaft. Untersuch.No.il, Dec., 1900. 



AN1) NITROCELLULOSE POWDERS 


5 



Apparatus for Kl-Starch Test. 


Fig. i 








6 


STABILITY TESTS FOR NITROCELLULOSE 


(2) Traces of unstable nitro-compounds (other than nitrocel¬ 
lulose) would show a product in which they are found by this 
test to be bad ; yet these traces of comparatively unstable com¬ 
pounds might not cause a decomposition of the explosive if kept 
under ordinary conditions. And, considering that there is no 
indication as to the effect of these traces of unstable compounds, 
this test does not indicate the keeping qualities of the explosive. 

(3) In cases of nitrocellulose powders, this test is affected by 
the solvents used in making the powders. 

(4) The weakest point of this test is that it can be masked by 
a number of substances which are sometimes added to the ex¬ 
plosive for this purpose. Mercury salts, especially mercuric 
chloride, are most frequently used for this purpose.* Accord¬ 
ing to Thomas,f HgCl., is reduced to Hg which unites with the 
oxides of nitrogen, preventing volatilization of the latter, and 
consequently retards the action on the test paper. A test paper 
which shows discoloration is readily bleached when exposed to 
vapors of mercury. Samples of nitrocellulose have been received 
at this laboratory, which contained traces of metallic mercury 
which had been added as such, or had been reduced from a mer- 
cury salt. 

Amines, e. g ., urea, have been added to powders in order to 
mask or lengthen the stability test.;j; Amines react with nitrous 
fumes as follows : 

R. NH 2 + HONO = R. OH + N 2 + H, 0 . 

Small quantities of alkalies or carbonates are sometimes added 
to neutralize remaining traces of nitrating acids, and also to 
combine with nitrous fumes resulting from decomposition.§ 

Other substances used to mask stability are|| acetic ether, ace¬ 
tone, oils, vaseline, aniline. 

(5) The test is affected by the condition of the sample,^ size 
of grains or pieces, whether freshly prepared for testing or ex¬ 
posed to air, and by moisture content. 

I he presence, in a powder, of mercuric chloride, or alkali, or any other substance 
which might in any way mask or interfere with the heat test (Kl-starch) will be sufficient 
to cause its rejection.” Standard Methods of Chem. Tests, Ordnance Dept., U. S. Army, 
t Zeitschr. f. Angew. Chem., 1898, p. 1027. 

J Hoitsema : Zeitschr. f. Angew. Chem., 1899, p.705. 

'4 The value of alkalies or carbonates for increasing stability is a disputed point. Gutt- 
mann, (Zeitschr. f. Angew. Chem., 1897^.233) discourages this practice, contending that the 
real decomposition of a mti ocellulose soon develops more acid than can be neutralized by 
the small amount of added alkali. Under some conditions, alkalies saponify and decom¬ 
pose nitro-compounds. 

|| Guttmann : Zeitschr. f. Angew. Chem., 1897, p. 233. 

Guttmann . Zeitschr. f.Angew. Chem., 1897, p. 265, found that it required 8% minutes 
h eat ground cordite from 12 0 to 69%° C. 


AND NITROCELLULOSE POWDERS. 


7 


(6) Slight differences in test papers greatly affect the results 
of this test.* The test papers used by the Ordnance Depart¬ 
ment are made in large quantities by Eimer & Amend, of New 
York, according to specifications, thereby insuring greater uni¬ 
formity than if made at different laboratories in small quantities. 
Manufacturers who have contracts with the government are sup¬ 
plied with these test papers. 

(7) The personal equation of the operator enters as a factor in 
causing variations. It is no easy matter to decide just when 
there is “the first appearance of a brown line” on the test paper, 
or just when the line is of the same intensity as a standard. 

From what has been said, it must be apparent that this test 
has too many weak points to make it a reliable one. The Ord¬ 
nance Department condemns no powder on results of this test 
alone. 

THE ZINC-IODIDE STARCH TEST. 

This is a modification of the test just described, using zinc 
iodide instead of potassium iodide, and a temperature of 8o° C. 

Zinc iodide is more sensitive than potassium iodide,f and also 
acts as a preservative of the test paper. However, a greater 
sensitiveness is in no way an improvement of the Kl-starch test, 

and results obtained at this laboratory show that it is no more 
reliable than the original, having all the weak points of the latter. 

THE GUTTMANN DIPHENYL AM IN TES'r.J 

Instead of using potassium or zinc iodide test papers, Gutt- 
mann recommended a paper moistened with a solution of diph- 
enylamin in sulphuric acid. He claimed for his test the following 
advantages over the KI-starch test : 

(1) Not as sensitive. 

(2) Test papers more easily prepared. 

( 3) Masking substances do not interfere as much. 

The temperature used is 70° C, and nitrous fumes turn the 
colorless paper to a greenish-yellow and finally blue. 

Thomas says§ the diphenylamin test is unsatisfactory ; it may 
be masked by adding diphenylamin to the explosive to be tested. 
Guttmann himself admits that the blue color sometimes fails 
to appear. Moisture in the sample affects the test. Thomas as 
well as others failed to get a sharp end reaction. The test was 

* Cullen : Jour. Soc. Chem. Ind., 1901, p. 8. 

t Guttmann, in “ Ch. Tech. Untersuchungsmethoden ” Lunge, II p. 492, says zinc iodide 
test paper is about l /$ more sensitive than potassium iodide paper. 

J Zeitschr. f. Angew. Chem., 1897, p. 233. Jour. Soc. Chem. Ind., 1897. p. 283. 

\ Zeitschr. f. Angew. Chem., 1898, p. 1027. 


8 


STABILITY TESTS FOR NITROCELLULOSE 


t 


tried at this laboratory but gave unsatisfactory results and was 
discontinued. Thomas, Aspinwall,* Spiea,| found sufficient ob¬ 
jections, after trial, to discard it. Major Nathan says J the test 
fails when testing volatile explosives, such as nitroglycerin, the 
latter being decomposed by the sulphuric acid on the test paper. 

THE HESS TEST. § 

Hess heated nitrocellulose to 70° C in a tube, and, by means 
of a current of air, the volatile products of decomposition are 
carried into a dilute solution of Kl-starch. Five observations 
are made : four colorimetric readings on the Kl-starch solution, 
and the time required for explosion of the sample. This test 
shows the beginning, and roughly and for a short time also how 
decomposition proceeds. The Kl-starch solution, like the Kl- 
starch papers, is far too sensitive, and has the weak points men¬ 
tioned under the “Kl-starch test”. 

THE HOITSEMA TEST.|| 

Another test in which an attempt is made to show the progress 
as well as beginning of decomposition. The explosive is heated 
for fifteen minutes at a constant temperature, and then, by 
means of a current of carbon dioxide, the volatile products of 
decomposition are passed through glass wool moistened with 
Guttmann’s diphenylamin solution. The operation is repeated, 
lowering the temperature io° each time until a temperature is 
found at which no decomposition takes place, i. e., at which no 
products of decomposition are formed which give a color reac¬ 
tion with the diphenylamin. 

This test is subject to most of the objections mentioned under 
the previous tests, especially the Guttmann test. As far as the 
writei* knows it is not in use in this country. 

THE EXPLOSION TEST. 

For this test o. 1 gram of the explosive is placed in a strong, 
wide test tube (see fig. 7 D) which is then lightly corked and 
placed in a paraffin bath at ioo° C. The bath (see fig. 2) is 
stirred and he ated so that the temperature rises 5 0 a minute un¬ 
til the sample explodes : the temperature at which this takes 
place is noted. 


* Jour. Soc. Ch. Ind., May 31, 1902. 
t Rivista, August, 1899. 
t Jour. Soc. Ch. Ind., 1901, p. 10. 

\ Dingier Polyt. Jour. 234, p. 43. 

|| Zeitschr. f. Angew. Chem., 1899, p. 705. 



AND NITROCELLULOSE POWDERS. 


9 


A good nitrocellulose should not explode under 186 0 C. 

A good nitrocellulose'powder should not explode under 177 0 C. 
A good nitroglycerin powder should not explode under 170° C. 



Fig. 2. Apparatus for Explosion Test. 

Experience shows that this test is reliable when the explosive is 
either very good or very bad, and is only a rough guide as to sta¬ 
bility. Variations in conducting the test give widely differing ex- 










io 


STABILITY TESTS FOR NITROCELLULOSE 


plosion points, especially if the temperature 
ent rate than 5 0 a minute. 


is raised at a differ- 


TUK THOMAS TEST.* 


The sample is heated in a glass-stoppered tube, in an oil bath, 
for eight hours daily. A good nitroglycerin powder should 
stand four days heating at 94-96° C, without developing brown 
fumes (N 2 0 4 ) ; a good nitrocellulose and nitrocellulose powder 
should not show fumes before three days, at a temperature of 
99-101° C. 

These temperatures are too low to produce a decomposition 
which may be accurately observed by the appearance of brown 
fumes ; it is difficult sometimes to say just when brown fumes 
appear. Moisture and volatiles in the sample affect the result. 
Aspinwallf objects to the length of time (sometimes over twenty 
days) required to obtain results. 


THE 1 35 ° C. GERMAN TEST. 

2.5 grams of the sample to be tested are placed in a strong 
test tube (see fig. 7 C) ; a piece of blue litmus paper is put into 
the tube about one-half inch above the explosive. The tube is 
lightly corked and placed into a bath (see fig. 3) at 135° C. 

Three observations are made : (1) reddening (complete) of the 
litmus paper, (2) appearance of brown fumes (N 2 0 4 ) and (3) ex¬ 
plosion of the sample. Stable explosives should stand the test as 
follows : 



Litmus red 

n 2 o 4 

No expl 

Nitrocellulose 

=30 

: 45 

5:00 

Nitrocellulose 

powder 1:15 

2:00 

5:00 

Nitroglycerin 

powder :3o 

:45 

5:00 


To make the results of this test as valuable as possible, all 
three observations must be carefully studied and compared with 
those obtained from known good powders. 

The temperature 135° is usually considered too high for sta¬ 
bility testing, as it may cause decomposition not always depen¬ 
dent upon the stability of the explosive. Sometimes it is impos¬ 
sible to say just when the litmus paper is red, or when brown 
fumes are present, and two operators may vary thirty minutes *y 
in their observations. Different makes of litmus papers give 
widely varying results. The test papers used by the Ordnance 
Department are made by Einer & Amend, according to specifi¬ 
cations, of as nearly uniform quality and sensitiveness as possible. 


* Zeitschr. f. Angew. Chem., 1898, p. 1027. 
t Jour. Soc. Ch. Ind., May 31, 1902. 



AND NITROCELLULOSE POWDERS. 


I I 



Fig. 3. Apparatus for German 135 0 C. Test 































































STABILITY TESTS FOR NITROCELLULOSE 


1 2 


By keeping all conditions as nearly uniform as possible and observ¬ 
ing' precautions mentioned, this test is one of the best of its kind. 

THE VIEI I.LE TEST ( I I O 0 c). 

Ten grams of the explosive are placed in a strong glass tube (see 
fig. 7 B), a piece of blue litmus paper is placed above the sample and 
the tube closed air tight ; the tube is then heated in an air bath* at 
i io° C (see fig. 4) until the litmus paper is completely reddened. The 
time required for this reddening is noted, the bottle removed and 
opened ; this operation is repeated daily, using a clean bottle and fresh 



Fig. 4. Apparatus for Vieille Test. 

test paper, until the time required to redden the paper is one hour or 
less. These daily times are added and the total (accumulated time) 
should not be less than 

30 hours for large grain powders, 

20 hours for small grain powders (5 inch or less), 

10 hours for nitrocellulose. 


* A special air bath is used to heat the samples to no°C; for description and illustration see 
Sy : Jour. Franklin Inst., March, 1903. 










AND NITROCELLULOSE I’OWDERS. 


>3 


This test is not applicable to nitroglycerin powders. In com¬ 
mon with all other heat tests where blue litmus paper is used, it 
shows only acid products of decomposition. It is practically im¬ 
possible to get all the bottles equally tightly closed, and on this 
account there are variations in time, since pressure is an impor¬ 
tant factor in decomposition—the greater the pressure the less 
the stability time. The personal equation of the observer in 
reading the reddening of the paper, and different makes of test 
paper give rise to variations. At this laboratory (Ordnance 
Department, U. vS. Army) the test papers used are the same as 
those described under the “135 0 C. Test”. 

THE WILL TEST.* 

Nitrocellulose is decomposed by heating to 135 0 C, and by 
means of a current of C0 2 , the products of decomposition are 
carried into a reduction tube containing a heated spiral of copper 
gauze ; here the nitrogen compounds are reduced to nitrogen 
gas which is measured over sodium hydrate solution. The nitro¬ 
gen is measured at regular intervals, and the rate of evolution is 
taken as an index of the decomposition. A nitrocellulose which 
by this test gives off equal quantities of nitrogen in equal inter¬ 
vals of time is considered by Will to be in “the limit state of 
purification,” and therefore as stable as possible. An unstable 
nitrocellulose—one not in the “limit state” (Grenzzustand)— 
suffers, at first, an accelerated decomposition, which sooner or 
later becomes uniform. 

Will’s test was thoroughly tried by Mr. C. P. Beistle, of the 
Frankford Arsenal laboratory, no expense nor time being spared 
in setting up the rather elaborate apparatus required, and in 
conducting the test. The results obtained were unsatisfactory 
and failed to distinguish a bad from a good nitrocellulose, and 
the test was abandoned. This test, as well as modifications of it, 
have been investigated in several laboratories in this country, 
but in all cases eventually discarded as impracticable. 

The following reasons are given as the cause of unsatisfactory 
results : 

(!) 135 0 C is too high a temperature for stability-testing pur¬ 
poses. 

(2) Decomposition is measured only by the nitrogen evolved. 

(3) From Professor Will’s experiments and diagrams it is not 
at all clear where to draw the line between a stable and an un¬ 
stable product. 


* Mittheilungen a . d. Centralstelle f. Wissenschaft. Untersuch. December, 1900, Neu Ba- 
belsberj?, Also abstr. in Jour. Soc. Ch. Ind., June 30, 1900. 





STABILITY TESTS FOR NITROCELLULOSE. 


(4) The statement is made in Professor Will’s report that for 
a certain nitrocellulose, heated for thirty hours and losing one- 
fourth its original nitrogen, the evolution of nitrogen in equal 
intervals of time was identical ; while in another place it is 
stated that 10 grams of nitrocellulose gave four times the amount 
of nitrogen that was given off by 2.5 grams. This latter state¬ 
ment is correct, judging from our own experiments, but it con¬ 
tradicts the former, since the amount of unchanged nitrocellu¬ 
lose in the former experiment is constantly deci easing. 

(5) It is practically impossible to buy or make C 0 2 which is 
free from air ; and as it is difficult to pass C0 2 through the ap¬ 
paratus at a uniform rate, the air-content of the gas gives lise to 
serious errors and if the current is too rapid it may cool the 
sample, and it, the C 0 2 , will not be completely absorbed by the. 
sodium hydrate solution ; if too slow, the gases of decomposition 
are not carried away fast enough, which may affect the decom¬ 
position, as stated by Professor Will. 

(6) If the reduction tube and copper spirals are not hot 
enough, or the C 0 2 passed too fast, some of the products of de¬ 
composition may escape reduction. 

(7) Unstable products are liable to explode which might cause 
considerable annoyance both to the operator and the apparatus. 

THE NEW TEST, I 15 ° C. 


From one to four whole pieces of powder are weighed on a 
watch glass and heated for eight hours in an air bath regulated 
to 115 0 C (-|- or — 0.5 0 ) ; the sample is then taken out, allowed 
to cool in a desiccator and weighed. This is repeated for six 
days, at the end of which time the total loss of a powder must 
not exceed 8 per cent. 

A specially constructed air bath is used for obtaining a uni¬ 
form temperature. The apparatus, shown in figs. 5 and 6, con¬ 
sists of a doubled-walled, sheet copper oven like the water ovens 
in general use, except that the new oven has the inner bottom 
slightly V-shaped (fig. 6, d) : this effectively prevents bumping. 
Between the walls the oven is filled (about two-thirds full) with a 
mixture of xylol and toluol in such proportion that when the mix¬ 
ture boils, the air in the oven has a temperature of 115 0 C. A 
reflux condenser prevents the evaporation of the xylol-toluol. 

In developing the new test a great deal of experimental work 
was necessary (credit is due Captain Dunn for suggestions and 
aid in this work). The points to be decided were : 1. Does de¬ 

composition increase as the temperature increases? 2. Does a 
bad powder decompose more rapidly than a good one? 3. Which 
is the most suitable temperature for the new test? 


AND NITROCELLULOSE POWDERS 


l 5 



Fig. 5 


Oven for New 115 0 Test 











STABILITY TESTS KOK NITROCELLULOSE 


I 6 



Fig. 6 . Oven for New 115 0 C. Test 
































































A B C D 

Fig. 7 . A. Arrangement of tube and sample for Kl-starch test. 

B. Arrangement of tube and sample for Vieille test. 

C. Arrangement of tube for German 135 ° C test. 

D. Arrangement of tube for Explosion test. 


























AND NITROCELLULOSE POWDERS. 


*7 

Decomposition increases with the temperature ; this is shown 
in figs. 8 and 9, showing the loss in weight of powders Nos. 179 
and 391 respectively when subjected to different temperatures. 
Experiments soon showed that a bad powder decomposes much 
more rapidly than a good one. As may be seen from figs. 8 and 
9, decomposition at ioo° C is very slow ; at no° it increases but 
requires too much time to show a decided difference between 
good and bad powders. At 115 0 decomposition is still further 
increased and big differences are shown between good and pow¬ 
ders in a reasonably short time, see figs. 11, 12 and 13. In fig. 
11, powders 265, 293 and 391 are bad; in fig. 12, Nos. 803, 344 
and 546 F.A. are bad ; in fig. 13, Nos. 4-25, 405, 406 and 326 are 
bad. All other powders shown are good. 

Experiments were made at 120° ; at this temperature powders 
decompose more rapidly than at 115 0 , but the difference between 
a good and a bad powder is not as great, all powders decompos¬ 
ing more or less rapidly. 

Although it is desirable to shorten the time of a test, yet it is 
undoubtedly of greater value the nearer the temperature ap¬ 
proaches that of ordinary conditions of storage and handling. 

The effect of size of grain on the decomposition is shown in 
fig. 14. Powders 922, 924 and 926 were made from the same ni¬ 
trocellulose and as nearly alike as possible except in size, being 
for 8, 10 and 12-in. guns respectively. Decomposition increases 
but very slightly with size of grain, probably d*ue partly to a 
slightly higher content of moisture and volatiles, and partly to 
internal pressure of products of decomposition from the larger 
grains. Powders 391 and 546 F.A., fig. 14, are bad and are 
shown for comparison with the good powders 922, 924 and 926.* 

Experiments were made to shorten the time of the new test 
by sealing the samples in tin boxes and thus effecting decom¬ 
position under pressure and determining the combined effect of 
heat and pressure. 

The weighed samples were sealed up (soldered) in small tin 
boxes and then exposed to 8o° and ioo° C., opened at regular 
intervals and weighed. At 8o° decomposition is slow but con¬ 
siderably greater than if heated in the open. At ioo° (sealed) 
decomposition proceeds quite rapidly, being almost as great as 
at 115 0 in the open. The difference between a good (577) and a 
bad powder (391) nt ioo°, sealed and open, is shown in fig. 15* 
The effect of pressure is the same as an increase of temperature. 
Further experiments are to be made along this line of testing. 

* For further data see “Jour. Am. Chem. Soc.,” June, 1903. 


18 


STABILITY TESTS FOR NITROCELLULOSE 


After applying* the new test to a large number of powders it 
was found to give more reliable results than any other test now 
in use. It has the following advantages : 

(1) The powder is tested in its -natural condition , the same in 
which it is stored or used. 

(2) It shows all products of decomposition ; the older tests 
show only acid products , or only nitrogen as in the Will test. 

(3) It shows the decomposition of nitro-compounds other than 
nitrocellulose which are often present in a powder, and also shows 
the effect of this decomposition on the powder itself. 

(4) It shows the effect on the stability of a powder of added 
substances (for masking stability) ; the effect of volatiles : hand¬ 
ling and working which may set up local decompositions ; traces 
of nitrating acids ; decomposition due to saponification by water, 
alkalies, carbonates, etc. 

(5) It shows quantitatively the progress of all decomposition. 

(6) The test itself as well as the apparatus used is simple and 
not subject to variations like the old tests. 




/fe? C£A/r Loss, 


19 






















































































































Pea Ce/-Jt Loss. 


20 


8 Hour Da ys. 



\ 











































































































2 I 


24 Hour Days. 



Fig. io. 














































































































Per Cent Loss 


22 


8 Hour Days. 





Fig. ii. 
























































































































Per Cent Loss 


2 3 


8 Hour Days. 



•si *OIjJ 































































































































24 


8 Hour Days. 



Fig. 13. 
























































































Per Cent Loss, 


2 5 


8 Hovft Days. 



% 

a 
















































































Pbh C£tfr Loss. 


26 


24 Moa/? Da ks. 





Fig. 15. 






















































































